The present invention relates to rotary switches and, more particularly, to a rotary switch having a detent mechanism.
The trend toward smaller electronic components has created a need to achieve functional equivalents of larger components with fewer parts thereby facilitating ease of assembly and reducing size and cost. In a miniature switch, the detent mechanism typically requires a plurality of parts and occupies valuable space. The reduction in size of rotary switches and particularly the detent mechanism of the switch presents problems attendant with a scaling down of size.
As the size of a switch is arithmetically reduced, the structural strength of the components of the switch is exponentially reduced. The prior art, as exemplified by U.S. Pat. Nos. 3,300,594 and 3,699,279 describes difficulties associated with miniature switches.
The prior art, as exemplified by U.S. Pat. No. 3,196,237, also shows a switch having a detent member in a segment of a portion of the switch housing. In such devices, the cammed rotor, when engaging the detent member, imparts a torsional moment to the detent member thereby increasing the stresses within the material of the supporting arms. These generated torsional stresses require that the supporting arm be less resilient to withstand the torsional stresses and thereby necessitates a reduction of the desired resilient characteristic. It is, therefore, desirable to provide a detent for a miniature rotary switch having an intermediate member disposed between the cam and the resilient member partially to insulate the resilient member from generated torsional force and thereby reduce the stress within the resilient member. It is further desirable that the intermediate member be integrally formed from the housing and maintained in position without necessitating additional parts and cost thereof.
As the siize of a switch is reduced and the forces generated by the detent members are not decreased proportionately, increased material stresses are encountered. When a rotor exerts pressure on a detent cam, an opposing pressure is exerted by the cam against the shaft of the rotor and the rotor support bearing. A small diameter shaft rotating in an appropriate diameter bearing presents a small bearing surface for withstanding the detent pressure. The prior art switches, as disclosed in patent application Ser. No. 496,973, issuing as U.S. Pat. No. 3,968,338 on July 6, 1976 assigned to the same assignee as the present invention, overcome this problem for a single-pole doublethrow switch wherein an actuator having a cam directly actuating the movable contact of the switch is supported by a rim of the housing. Such construction of the detent cam directly actuating the movable contact of a single pole switch has limited application. It is, therefore, desirable to provide a miniature multiposition rotary switch wherein the detent forces applied to the rotor are applied over a large bearing area thereby substantially reducing the stress therein.
In certain applications, the output of a rotary switch is indicative of the angular position of the rotor. A rotary switch having a binary coded output is ideally suited for a logic function control in machine tools, test equipment or the like. The prior art, as exemplified by U.S. Pat. No. 3,699,279 describes a switch having a coded output accomplished by a sheet of insulating material, such as mylar, provided with apertures therein at predetermined locations to permit selective electrical contact between the stator and the contactor upon rotation of the rotor. A coded output for a switch can also be achieved by arrangement of stator conductors to provide the coded output. Such stator conductors are produced either by an etching conductive material from a printed circuit insulator or the like, or by precise depositing of an intricate conductor upon a suitable stator material. It therefore would be desirable to provide rotary switches with a coded output that can be produced in a simple and facile manner.
Accordingly, it is an object of the present invention to provide a rotary switch with an improved detent. A further object of the present invention is to provide a miniature rotary switch wherein the stresses caused by the detent forces are minimized. Another object of the present invention is to provide a miniature switch wherein the periphery of the rotor is rotatably supported in a bearing. Yet another object of this invention is to provide a rotary switch wherein the detent utilizes a resilient portion of the housing. A further object of the present invention is to provide a rotary switch having a binary coded output.
Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.
Briefly, the present invention relates to a multiposition rotary switch having an improved detent mechanism and wherein a coded output is provided with a minimum of extra parts. The detent mechanism includes a cam integral with a rotor flange which in turn is rotatably supported by an annular bearing formed from the housing acts through a cam follower to deform resiliently a portion of a side of the housing. A contactor constrained to rotate with the rotor wipably engages a plurality of contacts carried on a base member. In an alternate embodiment, insulating means such as glass is deposited on portions of the arcuate conductors at predetermined locations thereof selectively to insulate electrically the contactor from the conductors thereby providing a coded output indicative of the angular position of the rotor.